Sound recording and reproducing means



Feb. 14, 1933. K DAHMEN I 1,897,722

SOUND RECORDING AND REPRODUCING MEANS Filed April 29,1951

Fig.4.. f as 4O a g 3 35 4 41 Jnveni'or: (4R4 Dal /M5 A'Hornoys PatentedFeb. 14,1933

UNITED STATES: PATENT OFFICE:

KARL DARREN, Ol DUSSELDOBF, GERMANY SOUND RECORDING AN REPRODUCING HEARSI Application filed April 29, 198i, Serial No.

This invention has reference to a method of recording acoustic signalsby electro-mag netic means and it is one of the important objects of theinvention to produce acom paratively large or extensive record in a verysimple manner upon a com aratlvely small carrier, 8. plurahty of sucrecords being superimposed upon each other in the well known manner.With the methods heretofore in use for the production of acousticrecords there was the inconvenience that the tion or of spacing thecoils for each record,. 2 so that the number of the records to besuperimposed had to be restricted from constructional reasons.

N ow with the method of the invention to be described it becomespossible however to 'arrange an almost unlimited number of records in acomparatively small space. Broadly considered, this object isaccomplished by producing two records of each acoustic signalsimultaneously the intensity of which varies however in accordance witha certain freuency. Furthermore, the intensity curves of tr e tworecords are displaced with relation,

to each other by a differentiated positioning of their periods, so thatfor each phase the sum of each two recording intensities of equaltime-periods remains the same, that is to say,

' that the resulting intensity is constant. For

each of the superimposed records a different frequency of thefluctuations of intensity is $5 to be selected, while the velocity ofthe recording carrier relatively to the record producing member remainsconstant.

The invention will be more fully described bly reference to theaccompanying drawing s owing an exemplification embodying the wheels538,711, and in Germanylarch 80, 1929. I

principles of this invention in perspective view, all the details of thesupporting frame and of the means which do not constitute a part of theinvention, and are unnecessary for the understanding thereof not havingbeen shown in the drawing.

In the drawing: r

Fig. 1 shows diagrammatically a sound recording and reproducing device.

Fig. 2 1s a perspective view of a part of the device. The modificationshownin the drawing comprises two previously magnetized steel bands 1situated side by side and wound on rollers 23, one of whichis shown inFig. 1 The bands 1 pass over a" guide 1-oller 2 and are wound on rollers24. The rollers 23 and 24 are rotated by means of electrical motors 25and 26 which are connected with a main 31 .by conduits 27 and'28, whilethe wirings 29 and 30 connect said motors with a return line 32. Aswitch 33, 34 is used to connect either the motor 25 or the motor 26with a source of electrical energy not shown in the drawing, one of themotors being cut off from the supply of electricalcurrent while theothermotor is in operation. In the position shown in Fig. 1 the mainlines 31 and 32 are connected with the motor 26 .drivingthe. rollers24.so

that the bands 1 will be moved in the direction of the arrows shown inFigs 1 and '2, and will be wound on said rollers 24. By switching theswitch 33, 34 to its other position, shown'by dotted lines in Fig. 1, itispossible to wind the bands 1 back on the rollers 23. A wire 35connects the main line 31 with resistances 36 and 37, which can beregulated by levers 38 and 39. Conduits 40 and 41 connect theresistances 36 and 37 with electrical motors 42 and43. which are. connected with the return line 32'by means of M 'the conduit 44. -Theelectrical motor 42 drives a shaft 7 by means of a cord 45 passingaround a grooved wheel 8 rigidly connected with said shaft. Two cords 46and 47 connect the electrical motor 43 with grooved 17 and 18 and drivethe adjustable resistances 13 and 14 connected with said wheels. Twocoils 3 and 4 are situated over the bands 1 at the placewhere thesebands pass over the roller 2, said coils. being conactuate the arms 5and 6, so that the magnets 11 and 12 connected with the arms 5 and 6,and situated within the coils 3 and 4, alternately. approach and recedefrom the bands ,1. Itis to be notedth at the magnets 11 and 12 shouldhave a polarlty different from that of the bands 1. A sliding contact 15is situated over the adjustable resistance 13 driven by a wheel 17 andforms an angle of 180 with a sliding contact 16 situated over the ad- 15justable resistance 14, which is driven by the wheel 18. The resistances13 and 14 are connected with the lower ends of the coils 3 and 4 bymeans of wires 19 and 20, while the upper ends of the coils 3 and 4arevconnected with one of the leads 21 of the talking circuit. The otherlead 22 is connected with the sliding contacts 15 and 16.

During the reception of the acoustic signals the sliding contacts 15, 16are uniformly rotated, so that due to the resistances 13 and 14, aweaker or a stronger current impulse will be produced in the coil 3-andthen in the coil 4, so that either one or the other of the bands 1 willbe submitted to a stronger or a weaker action of the magnets, while thetotal intensity of the magnetic influence remains always the same. Atthe same time,

however, said magnets 3 and 4 are alternatingly moved by the cams 9, 10,so that they will come closer or less close to their corre-' spondingsteel bands 1. The bands 1 are provided with records of sounds alongtheir entire length while being wound on the rollers 24. Then theposition of the switch 33, 34 is changed and the bands 1 are again woundon the rollers 23. The recording which takes place during this secondwinding is superimposed on the previous records, so that saidsubsequentrecording must take place with a frequency different from thatof the previous records. changing the position of the levers 38 and 39of the resistances 36 and 37, since it will correspondingly change thevelocity of rotation of the sliding contacts 15 and 16 and of the cams 9and 18. By a suitable selection of the rotating speed of the slidingcontacts 15, 16 and of the cams 9, 10 there is the possibility for theproduction of a'large number of different frequencies, and consequentlyof a larger number of records to be superimposed. The reproduction ofsuch records should, of course, take place under the same operatingconditions. 1

It should be understood that the invention is not limited to theembodiment herein shown and described merely by way of exemplification,and other means may be used for the production of the modulatingfrequencies, as long as the essential features of This is easilyobtained by the invention remain unchanged which are constltuted by thefact that several records may be obtained by different frequencies upon.the same carrier, which are then reproduced under the same conditions.

I claim:

'1. A method of recording acoustic signals, comprising the steps ofproducing two records for each acoustic signal, each of said recordshavlng a time period and intensity different from that of the otherrecord produced by the same signal, the sum of the intensities of tworecords produced by the same signal having a constant value, andsuperlmposlng records having a different frequency of fluctuations ofintensity.

2. A method of recording acoustic signals,

comprising the steps of producing by"electro-magnetic means two recordsfor each acoustic signal on a recording element, passing phase displacedelectrical currents through said electro-magnetie means during therecording of said acoustic signal, and then superimposing records havinga different frequency from that of the first-mentioned records on saidrecording element.

3. A device for recording acoustic signals, comprising a pair ofmagnetized bands, means for synchronously movingsaid bands, a pa r ofelectro-magnets situated near said bands, means for alternatelyreciprocating said magnets, a talking circuit connected with saidmagnets, resistances connected with said magnets, and means forproducing a phase diiierence'in one of said resistances.

4. A device for recording acoustic signals, comprising a pair ofmagnetized band's,

means for synchronously moving said bands,

a pair of electro-magnets situated near said bands, means for connectingsaid magnets in parallel, means for alternately reciprocating saidmagnets, a talking circuit connected with said magnets, a pair ofresistances, means for connecting said resistances in parallel with saidtalkingcircuit, one of said resistances having a phase displacement of180 degrees with respect to the other resistance, and means foroperating such resistances.

In testimony whereof I aflix my signature.

KARL DAHMEN.

